We use \(\bf m \odot e\)  to denote the final masked tokens as Eq (REF ). Follow the BERT [1]}, the masked regions are filled with a learnable mask embedding \([\text{MASK}]\) . Our strategy can ensure the patches with the highest scores are always presented (in Figure REF ).
\((\bf m \odot e)={\left\lbrace \begin{array}{ll}[\text{MASK}], & m_{i} = 1 \\e_i, & m_{i} = 0\end{array}\right.}\) 
